Potential methods for the fabrication of high-Tc superconductors for wires and cables

Studies of practical properties, such as upper critical field (H_C2) and critical-current density, of high-T _c oxide superconductors of Y-Ba-Cu-O Bi-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O systems are reviewed. The H_c2 of these materials is much higher than that of conventional metallic superconductors, indicating a high potential for practical applications, even when they are used in liquid nitrogen. However, the H_C2 of these materials is also highly anisotropic, as can be expected from an examination of their crystal structure. In addition to this anisotropy, the presence of weak links and a weak pinning force in this material limit the transport current density J₃ to much lower levels than that required for practical applications. Recent fabrication processes that have good potential for producing wire or tape conductors or high-T_c oxide are reviewed. Some details are presented of the powder method and other fabrication processes using diffusion, solidification, and deposition techniques. For the Ag-sheathed oxide tapes, J_c values exceeding 10000 A/cm² at 77 K and 0 T have been reported for both Bi and Tl oxide materials